Neuroscience Letters, 119 (1990) 27-31 27 Elsevier Scientific Publishers Ireland Ltd. NSL 07244 Lack of age effects on human brain potentials preceding voluntary movements Jaswinder Singh, Robert T. Knight, David L. Woods, Dennis J. Beckley and Clay Clayworth Department of Neurology, University of California, Davis, Veterans Administration Medical Center, Martinez, CA 94553 (U.S.A.) (Received 5 March 1990; Revised version received 8 June 1990; Accepted 17 June 1990) Key words: Readinesspotential; Bereitschaftspotential;Movement-related potential; Aging; Supplementarymotor area We examined age effectson Movement related potentials (MRPs) in 13 young (mean age = 29.3 years) and 13 old (mean age = 67.2 years) normal adults in right, left and bimanual self-pacedbutton press conditions. Both the groups generated a slowly rising readiness potential (RP) at about 1000 ms, a negativeshift (NS') at about 450 ms and a motor potential (MP) at about 100 ms prior to movement.The RP was symmetrical,bilaterally distributed and maximal at the vertex in all conditions in both the groups. Both the groups produced contralateraUyenhanced NS' and MP compo- nents in unimanual conditions. In contrast to prior reports, topographical distribution, onset latency and mean amplitude were comparable between young and old subjects for the RP, NS' and MP components of the MRP. The results indicate that motor programming as indexed by MRPs is unaffected by normal aging. The Bereitschafts- or readiness potential (BP or RP) is a slowly rising negative DC shift recorded prior to a voluntary motor act [9, 13]. The RP onsets several hundred milliseconds (typically about 1000 ms) before movement and is bilaterally symmetrical over pre- and postcentral regions. A negative potential maximal con- tralateral to movement (negative shift, NS') onsets at about 400 to 500 ms before EMG activity [17, 18]. The more variable pre-motion positivity (PMP) is bilaterally symmetrical and onsets between 80 and 90 ms prior to EMG onset [9]. The motor potential (MP) is maximal over the hemisphere contralateral to movement in unimanual motor tasks and onsets between 80 to 100 ms prior to movement [18]. A large positive potential is generated post-movement (P2). The RP and NS' repre- sent preparatory processes preceding movement initia- tion [12, 17] and may be generated by summed activity from supplementary motor area (SMA), premotor and sensorimotor cortices [16]. The signal to initiate motor activity may be indexed by PMP. The MP may be gener- ated by summated neural activity in motor cortex pyra- midal cells [19]. Movement related potentials (MRPs) have been pri- Correspondence: J. Singh, Department of Neurology, University of California, Davis, Veterans Administration Medical Center, 150 Muir Road, Martinez, CA 94553, U.S.A. marily studied in young subjects. RP and PMP ampli- tude are reported to decline in normal controls over forty years of age [1, 5, 7]. However, absence of signifi- cant age effects on the RP have also been noted [14]. The present study systematically assessed age effects on MRPs. Twenty-six right handed, neurologically normal adults (15 male; age range = 20-78) were recruited as paid subjects. Thirteen subjects were categorized as young (7 male, age range = 20--40, mean age = 29.3, S.D. = 5.7 years) and 13 old (10 male, age range = 54- 78, mean age = 67.2, S.D. = 7.4 years). Subjects were further subdivided into 4 groups; group I (n = 8, age range = 20-29 years), group II (n = 5, age range = 30- 40 years), group III (n = 7, age range = 54-69) and group IV (n = 6, age range = 70-78). Subjects with his- tory of neurological or psychiatric hospitalization were excluded from participation. The oldest subjects (70-78 years) were in excellent health for their age and were active hospital volunteers receiving no medication. In- formed consent was obtained from all the participants. Recording procedures have been described previously [18]. Briefly, recording was conducted in a sound atte- nuated, air conditioned, dimly lit room with the subject seated in a comfortable chair. Subjects were given a pushbutton (two pushbuttons in the bimanual condi- tion) mounted atop a cycle handle grip. The subject was instructed to grasp the handle in the palm and briskly 0304-3940/90/$ 03.50 © 1990 Elsevier Scientific Publishers Ireland Ltd.